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Brown Trout

The Brown Trout (Salmo trutta) is one of the trout species in Vermont that is not native. It was introduced to Vermont during the late 1800s, and now there are spawning populations in most of the drainage basins in the state.

They are commonly found in rivers and streams. Fish & Wildlife Department personnel carefully choose the lakes and ponds in which they stock Brown Trout, as the fish tend to grow quite large in these habitats and eat many smaller fish, including other stocked trout.

Habitat

The Brown Trout typically inhabits the lower reaches of cold-water streams, characterized by deep, slow-moving pools and runs. It also thrives in larger lakes of sufficient depth to maintain cool water temperatures year round. The Brown Trout is more tolerant of warm water temperatures and pollution than other species of trout.

As with other trout species, water temperature is a major limiting factor for Brown Trout. Optimum temperatures range from 53°F to 66°F, although they can tolerate temperatures near 80°F for short periods of time. Brown Trout tolerate pH levels from 5.0 to 9.5 but the optimal range is between 6.8 and 7.8.

Optimal brown trout habitat in streams is characterized by:

50% to 70% pools and 30% to 50% riffle runs;

A rocky bottom in riffle-run areas with no silt;

A gentle-sloping stream with slow, deep pools;

Relatively constant stream flows;

Stable banks with a lot of plant growth; and,

Overhead cover where streams are wide and deep.

Reproduction

Brown Trout usually live for five to six years, although ages of eight and nine years are not uncommon in waters that are not frequently fished. They generally grow at faster rates and achieve larger sizes than Brook Trout or Rainbow Trout.

In Vermont streams, Brown Trout tend to reach 5-9 inches after two years, 8-11 inches by their third year, and 9-14 inches by their fourth year. Growth rates in lakes are typically faster, with three-year-old Brown Trout reaching 11-18 inches and four-year-olds averaging 13-21 inches in length. Relatively few Brown Trout older than four years have been collected in fishery surveys, but every year anglers catch some very large fish.

In Vermont streams, the male Brown Trout matures at two to three years of age and the female matures one year later. Some lake-dwelling strains may not mature until the fourth or fifth year.

Spawning typically occurs from late October through December, when water temperatures reach an optimum range of 44°F to 48°F. Lake populations must have access to suitable tributary streams to reproduce. They sometimes migrate considerable distances to reach tributaries or headwaters with well-oxygenated gravel at the tail of pools.

Although Brook Trout will exclusively select groundwater upwellings for spawning sites, these areas may or may not be used by Brown Trout. The female digs a well-defined redd or shallow hole, which takes several days. When she is finished, one or more males will join her to complete the fertilization of her eggs.

Optimal incubation temperatures range between 36°F to 55°F, but tolerable levels range from 32°F to 59°F. Like Brook Trout, Brown Trout eggs overwinter in the gravel. Incubation times vary from 148 days at 35°F (typical of Vermont streams) to 30 days at 57°F.

Young fish, called fry, emerge from the gravel after absorbing their yolk sacs. They disperse quickly, immediately establishing territories in shallow, low-velocity pools with rocky surfaces. This habitat is also preferred by larger juvenile Brown Trout, which may force the fry to the edges of pools and riffles on smoother surfaces.

Diet

Brown trout are opportunistic feeders, but are perhaps more selective than other trout species. Aquatic and terrestrial insects make up the primary food source of brown trout that are less than ten inches in length. As they become larger, they shift more to fish and crustaceans. Mature brown trout in streams feed primarily at night, while those in lakes are more likely to feed during daylight hours.

Management

In Vermont, over 180 lakes and ponds and 3,800 miles of streams and rivers are managed by the Vermont Fish & Wildlife Department for one or more trout species. The department must decide whether or not to stock an area, where to set length and creel limits and gear restrictions, and when and where to allow or not allow fishing by anglers.

The general areas the state considers in management are:

Habitat capacity, or quality and quantity of existing fish habitat in the water;

Fishing pressure, or how heavily people fish the area;

The productivity or food base of the stream, river or lake;

The present species of fish that are managed in the body of water;

Whether natural reproduction of the trout species would be supported;

Timing and duration of spawning runs;

Public input.

Steps the Vermont Fish & Wildlife Department make in managing trout in Vermont start with monitoring and evaluating the existing trout population. Biologists take care to protect the selected habitat of the trout and partner with others to implement restoration efforts according to their evaluations. After evaluating the stream, river or lake, they stock trout if needed.

Stocking is determined with one of their three techniques: "put-grow-take," "put-take," or "species recovery" (specific for Atlantic salmon).

Put-take: Catchable-size trout (greater than 6" and often 8-10" long) are stocked in areas where fishing pressure is high, but habitat does not support sufficient natural reproduction or growth of young fish to meet fishing demands. Put-take stocks are removed by fishing usually within one season. The fish that are not caught, rarely survive to the following season. This method of stocking is used primarily in rivers and streams.

Put-grow-take: Smaller-sized fish stocked in spring to "grow" to catchable size before being caught. Often used in ponds and lakes where fish can survive the winter and where adequate food is available for fish survival. This technique is usually used to maintain populations where spawning habitat is lacking.

Species Recovery: Stocking of fingerlings with the goal of reestablishing the trout species in a particular body of water.

Status

The brown trout was introduced to Vermont during the late 1800s and the species soon established a firm foothold in all the major drainage basins. It frequents many of the streams and rivers also occupied by brook trout and rainbow trout.

Brown trout have a preference for the deeper, slower and more fertile downstream river areas. Natural spawning populations are common to most drainage basins in the state, nevertheless, many of these waters are also stocked with catchable-sized brown trout to supplement the wild resource and improve fishing opportunities.

The establishment of wild brown trout populations in a large number of waters has often been at the expense of the native brook trout. For example, the Batten Kill in the southwestern region of the state was historically a brook trout stream, but the brown trout, introduced around 1926, have largely replaced the native species.

On the other hand, the establishment of brown trout populations has given anglers another type of trout to catch in Vermont. The brown trout is also well adapted to many lowland river areas, to which brook trout are not well suited. Brown trout often grow to trophy sizes in these waters.

Brown Trout populations in lakes and ponds are relatively limited in Vermont. Even though Brown Trout adapt well to certain pond and lake habitats, Vermont Fish & Wildlife Department has decided to only stock rivers and streams.

Brown Trout have a tendency to accumulate in abundance in lakes and ponds because they out compete other trout species and withstand fishing so well. They also tend to grow larger than other trout species and then feed heavily on other fish, including recently stocked smaller trout. Brook and Rainbow Trout do not pose such problems when they are stocked in lakes and ponds.